Various electronic apparatuses such as mobile phones and personal digital assistants (PDAs) have been widely used, and it has been demanded to further reduce size and weight of the electronic apparatuses and to achieve their longer lives. Accordingly, batteries, in particular, small and light-weight secondary batteries that have ability to achieve high energy density have been developed as power sources for the electronic apparatuses.
Applications of the secondary battery are not limited to the electronic apparatuses described above, and it has been also considered to apply the secondary battery to various other applications. Examples of such other applications may include: a battery pack attachably and detachably mounted on, for example, an electronic apparatus; an electric vehicle such as an electric automobile; an electric power storage system such as a home electric power server; and an electric power tool such as an electric drill.
There have been proposed secondary batteries that utilize various charge and discharge principles in order to obtain battery capacity. In particular, attention has been paid to a secondary battery that utilizes insertion and extraction of an electrode reactant, which makes it possible to achieve higher energy density than other batteries such as a lead-acid battery and a nickel-cadmium battery.
The secondary battery includes a cathode, an anode, and an electrolytic solution. The cathode includes a cathode active material involved in charge-discharge reaction, and the anode includes an anode active material involved in charge-discharge reaction. The electrolytic solution includes a solvent and an electrolyte salt. The configuration of the secondary battery exerts a large influence on battery characteristics. Accordingly, various studies have been conducted on the configuration of the secondary battery.
More specifically, in order to achieve superior battery characteristics, a metal-based material such as silicon is used as the anode active material, and, for example, an unsaturated cyclic carbonate ester is used as an additive of the electrolytic solution (for example, refer to Patent Literature 1). Moreover, in order to suppress expansion and contraction of the anode during charge and discharge, a mixture of an alloyed material and a carbon material is used as the anode active material (for example, refer to Patent Literature 2).